An aneurysm occurs at a weak point in the wall of a blood vessel (artery). Because of the flaw, the artery wall bulges outward. This bulge is called an aneurysm. An aneurysm can rupture, spilling blood into the surrounding body tissue. A particularly dangerous type of aneurysm is a cerebral aneurysm. A common form of cerebral aneurysm is a berry aneurysm, so-called because of its shape. If a cerebral aneurysm ruptures, it can cause permanent brain damage, disability, or death.

A ruptured aneurysm spills blood into the brain or into the fluid-filled areathat surrounds the brain tissue. Bleeding into this area, called the subarachnoid space, is referred to as subarachnoid hemorrhage (SAH). Cerebral aneurysms can be caused by brain trauma, infection, hardening of the arteries (atherosclerosis), or cancer, but most seem to arise from a congenital, or developmental, defect.

Some aneurysms may have a genetic link and run in families. Better evidence links aneurysms to certain rare diseases of the connective tissue. Polycystickidney disease is also associated with cerebral aneurysms.

Cigarette smoking, excessive alcohol consumption, and recreational drug use (for example, use of cocaine) have been linked with an increased risk of aneurysm rupture. High blood pressure may be a risk factor but not the most important one. Pregnancy, labor, and delivery may increase the possibility of an aneurysm rupturing, but not all doctors agree.

Most aneurysms go unnoticed until they rupture. However, 10-15% are found because of their size or their location. Common warning signs include symptoms that affect only one eye, such as an enlarged pupil, a drooping eyelid, or pain above or behind the eye. Other symptoms are a localized headache, unsteadygait, a temporary problem with sight, double vision, or numbness in the face.

Some aneurysms bleed without rupturing, but symptoms may develop gradually. The symptoms include headache, nausea, vomiting, neck pain, black-outs, ringing in the ears, dizziness, or seeing spots.

Nearly 50% of patients who have aneurysmal SAHs experience "the warning leakphenomenon." Persons with warning leak symptoms have sudden, atypical headaches that occur days or weeks before the actual rupture. These headaches are referred to as sentinel headaches. Nausea, vomiting, and dizziness may accompany sentinel headaches.

When an aneurysm ruptures, most victims experience a sudden, extremely severeheadache. Nausea and vomiting commonly accompany the headache. The person may experience a short loss of consciousness or prolonged coma. Other common signs of a SAH include a stiff neck, fever, and a sensitivity to light. About 25% of victims experience problems linked to specific areas of the brain, swelling of the brain (hydrocephalus), or seizure.

Based on symptoms, a doctor will run several tests to confirm an aneurysm oran SAH. A computed tomography scan (CT or CAT) of the head is the initial procedure. The scan is most useful when it is done within 72 hours of a rupture.

If the CT scan is negative for a hemorrhage or if the diagnosis is unclear, the doctor will order a cerebrospinal fluid (CSF) analysis. Cerebral angiography can be used to map the brain's blood vessels and the damaged area.

The primary treatment for a ruptured aneurysm involves stabilizing the victim's condition. The patient may require mechanical ventilation, oxygen, and fluids. Medications may be given to prevent major secondary complications such as seizures, rebleeding, and vasospasm (narrowing of the affected blood vessel). Vasospasm decreases blood flow to the brain and causes the death of nervecells.

In general, surgical procedures are performed as soon as possible to preventrebleeding. The chances that aneurysm will rebleed are greatest in the first24 hours, and vasospasm usually does not occur until 72 hours or more after rupture. The preferred surgical method is a clip ligation in which a clip is placed around the base of the aneurysm to block it off from circulation.

Fifteen to twenty-five percent of people who experience a ruptured aneurysm do not survive. An additional 25-50% die as a result of complications associated with the hemorrhage. Of the survivors, 15-50% suffer permanent brain damage and disability. These conditions are caused by the death of nerve cells. Immediate medical treatment is vital to prevent further complications and braindamage in those who survive the initial rupture.

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